In recent years, there has been a demand to reduce the size of unmanned air vehicles. The Defense Advanced Research Projects Agency (DARPA) defines the class of air vehicles measuring 15 cm or less in any dimension as micro air vehicles (MAVs). Possible applications of these vehicles range from civilian and military surveillance to search and rescue operations. Numerous research groups are actively developing designs of new MAVs. Examples of MAVs include the Black Widow, developed by AeroVironment Inc., and the University of Florida's flexible wing design. Like the majority of MAVs, the above examples comprise scaled-down versions of larger traditional flying vehicles with fixed or rotary wings. Unfortunately, the Reynolds number and the aerodynamic lift of traditional flying vehicles decreases substantially as the wing length of the vehicles decreases.
Numerous research groups are attempting to solve the problem of low aerodynamic lift in MAVs by developing a class of MAVs known as ornithopters, or flapping wing vehicles. The flapping wings of animals, and potentially new flapping wing MAVs, rely on translational motion, referred to as “flapping,” and rotational motion, called “feathering,” of their wings to develop unusually high lift. Thus, there is an interest in designing a lightweight, compact mechanism that enables wing flapping in an ornithopter that is inspired from the wing motion of hummingbirds and hovering insects.